[Boatanchors] Relay Repair - Demagnetization Question

[Bob, W5UQ]

Glen is absolutely right.  In broadcasting, we ran across this 
periodically.  After we either degaussed the relay or reversed the 
leads, the relay would then cease to either stick or have a slowed down 
action. 

ALSO, note that a lot of DC relays have a diode across the coil for back 
EMF.  This can cause the relay to be sluggish, or slow to release.  The 
delay, in some cases, can cause a problem.  Usually it does not.  But if 
the circuit is such that the relay needs to drop out fast, then the 
slowed down action, even though it is in milliseconds, can cause other 
problems......so if one adds a diode, thinking it is a good thing, it 
may not be. 

Bob


Glen Zook wrote:
> In theory, yes.  But, unfortunately, in reality, no!  There are all sorts of relays "out there" that, when run from DC, definitely get magnetized.  The "fix" is to reverse the connections periodically.  Now when run from AC the problem doesn't exist.
>
> Glen, K9STH
>
> Website:  http://k9sth.com
>
>
> --- On Tue, 2/2/10, Ron <ronami at yahoo.com> wrote:
>
> Relays are designed with very low coercivity (or remnance) cores. There is no need to ever demagnetize a relay.
>
>
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